When hummingbirds fly unfriendly skies

Hovering behind a fat obstacle like a tree trunk on a windy day may have costs

HOVER MASTER  An Anna’s hummingbird can sip nectar in fairly bumpy air but may have to calculate when a meal isn’t worth the energy expenditure of fighting turbulence.

Matthew Field/Wikimedia Commons

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Swirling air can make hummingbirds work harder to hover, but only when the air’s vortices open wider than a bird’s wing.